Resistor Derating; Duty Cycle - ABB MicroFlex e190 User Manual

176 Resistor braking


Resistor derating

The brake resistors shown in the previous table can achieve their stated power rating
only when mounted on a heat sink. In free air a derating must be applied.
Furthermore, in ambient temperatures greater than 25 °C (77 °F), a temperature
derating must be applied.
Resistor part Nominal
number power rating
RGJ139
RGJ160
RGJ260
RGJ360
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Duty cycle

The braking duty cycle is the amount of time taken braking as a proportion of the
overall application cycle time. For example, the following diagram shows a system
which performs a trapezoidal move profile, with braking during part of the
deceleration phase. The braking duty is 0.2 (0.5 second braking / 2.5 second cycle
time):
v
2.5 s
(Cycle time)
In free air
(W)
100 Derate power linearly from:
80% @ 25 °C (77 °F)
70% @ 55 °C (113 °F)
200 Derate power linearly from:
300 70% @ 25 °C (77 °F)
62% @ 55 °C (113 °F)
Decel time
0.5 s
to
to
0.5 s
2.5 s
(Cycle time)
On heat sink
Derate power linearly from:
100% @ 25 °C (77 °F)
to
88% @ 55 °C (113 °F)
Typical heat sink:
200 mm x 200 mm x 3 mm
Derate power linearly from:
100% @ 25 °C (77 °F)
to
88% @ 55 °C (113 °F)
Typical heat sink:
400 mm x 400 mm x 3 mm
Braking active
0.5 s
2.5 s
(Cycle time)
t